Intermittent hypoxia activates temporally coordinated transcriptional programs in visceral adipose tissue.

Obstructive sleep apnea (OSA) is a prevalent disorder characterized by intermittent hypoxia (IH) during sleep. OSA is strongly associated with obesity and dysregulation of metabolism-yet the molecular pathways linking the effects of IH on adipocyte biology remain unknown. We hypothesized that exposure to IH would activate distinct, time-dependent transcriptional programs in visceral adipose tissue of mice. We exposed 36 mice to IH or normoxia for up to 13 days. We transcriptionally profiled visceral fat tissue harvested from the animals and performed functional enrichment and network analysis on differentially expressed genes. We identified over 3,000 genes with significant expression patterns during the time course of IH exposure. The most enriched pathways mapped to metabolic processes, mitochondrion, and oxidative stress responses. We confirmed the pathophysiological relevance of these findings by demonstrating that mice exposed to chronic IH developed dyslipidemia and underwent significant lipid and protein oxidation within their visceral adipose depots. We applied gene-gene interaction network analysis to identify critical controllers of IH-induced transcriptional programs in adipocytes-these network hubs represent putative targets to modulate the effects of chronic IH on adipose tissue. Our approach to integrate computational methods with gene expression profiling of visceral fat tissue during IH exposure shows promise in helping unravel the mechanistic links between OSA and adipocyte biology.

Genome-wide gene expression profiling in children with non-obese obstructive sleep apnea.

BACKGROUND: Obstructive sleep apnea (OSA) is a multi-factorial and highly prevalent disorder in which both genetic and environmental factors may be involved. If left untreated, OSA may lead to significant cardiovascular and neurocognitive and behavioral morbidities. We hypothesized that pediatric OSA would lead to altered gene expression in circulating leukocytes. METHODS AND RESULTS: Oligonucleotide-based microarray technology was used to identify mRNAs that may be differentially regulated in non-obese children with polysomnographically-established OSA compared to matched control children. Total morning blood RNA from 40 children (20 OSA and 20 controls) was extracted, labeled, and hybridized onto independent oligonucleotide-based microarrays. Of the 44,000 transcripts, 1217 transcripts were differentially expressed in OSA (p-value <0.05), with 68 transcripts (38 RefSeq accession numbers, 30 ESTs) fulfilling high stringency criteria. False Discovery rate (FDR) was used to determine the significance-difference of OSA vs. normal samples. Microarray data were further validated using quantitative RT-PCR techniques. Biological pathways pertinent to the differentially expressed genes were explored and revealed prominent involvement of inflammatory pathways. CONCLUSIONS: RNA derived from peripheral leukocytes confirms the presence of altered expression of functionally relevant gene clusters in pediatric OSA. Large-scale genomic approaches may provide further insights into adaptive and end-organ injury related mechanisms in the context of OSA in children.